here is what I am doing with the LEDs and you'll see why a smaller power supply is better than a larger one.
AA's would wrap around the perimiter better. But they add too much weight.
The 9v is smaller in weight and footprint size, but it doesn't really mount very well to the project and is bulky looking. I have single and double mounting brackets for the AA'a. But they are simply too heavy and too long to really work.